#define  _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
	    float x = 0;
		float y = 0;
		float z = 0;
        float average=0;
	    scanf("%f %f %f", &x, &y, &z);
	    average = (x + y + z) / 3.0;
	    printf(" % f\n", average);
	    return 0;

}